The present invention relates to catalysts for hydrotreating heavy oils including, as typical examples, topped crude and vacuum residue, in more detail relates to catalysts which are capable of achieving satisfactory results in the process of desulfurization, demetallization or denitrification and further in the point of yield of kerosene-gas oil fractions when used in hydrotreating heavy oils.
In recent years, as crude oils are becoming heavier and heavier, the techniques are becoming more and more important which comprise treating heavy oils containing high molecular weight such as asphaltenes, resins and further containing vanadium, nickel and the like in the form of organic metallic compounds, in the presence of catalysts and under hydrogen pressure and effecting desulfurization, demetallization or denitrification while cracking said heavy oils. On the other hand, with increase of the demand for kerosene-gas oil, there is a more increasing demand for obtaining kerosene-gas oil fractions, which are called the middle cut, in high yield in desulfurization, demetallization or denitrification processes of heavy oils while suppressing the by-production of gas components as much as possible when hydrotreating heavy oils. However, the fact is that it is extremely difficult for the usual hydrotreating catalysts to effect desulfurization, demetallization or denitrification of heavy oils to the fullest extent and further obtain kerosene and gas oil fractions in high yield.
That is to say, in hydrotreating heavy oils there have been normally used catalysts prepared by impregnating hydrogenation metals on the carriers comprising amorphous inorganic oxides and zeolite. The carriers of such catalysts are roughly divided into those consisting mainly of amorphous inorganic oxides and those consisting mainly of zeolite. The former displays high efficiencies in desulfurization, demetallization and denitrification (which will be called desulfurization and the like hereinafter) but it is difficult to obtain kerosene-gas oil fraction in high yield, while the latter, in contrast to the former, ensures a high yield of kerosene-gas oil fraction but does not always have enough activity for effecting desulfurization and the like. When the ratio of the amount of amorphous inorganic oxide to that of zeolite has been controlled properly, it results in that the activity of desulfurization and the like and the yield of kerosene and gas oil are both set at some low value.
To sum up, it is usual that in the conventional hydrotreating catalysts, since the improvement in activity of desulfurization and the like and the increase in yield of kerosene and gas oil contradict each other, for high activity in desulfurization and the like there are used catalysts which comprise mainly amorphous inorganic oxides in the catalyst carriers, sacrificing the yield of kerosene-gas oil fraction, while when aiming at a high yield of kerosene-gas oil fraction there are used catalysts of high content zeolite carriers, leading to some decreases in activity of desulfurization and the like.